Apparatus for carrying out well drilling operations from floating structures



Dec. 31, 1968 a... E. GILREATH APPARATUS FOR CARRYING OUT WELL DRILLINGOPERATIONS FROM FLOATING STRUCTURES Filed March 3, 1966 Sheet Dec. 31,1968 L. E. GILREATH 3,419,259

APPARATUS FOR CARRYING CUT WELL DRILLING OPERATIONS FROM FLOATINGSTRUCTURES Filed March 3, 1966 Sheet 2 0f 2 l I .Q I Q I l KL 1 i /IOO wi It N I 1 I i\ 80; \\\/4Z l i H I I: 84 I I) A I as 1 I 5 58 I y 1? r:

74 86 I fi I g 72 I I 70 50 e4\ 7 5o I 62- -46 J 4L7 E F7 INVENTOR.LAFAYETTE E. G/LREATH I BY United States Patent 3,419,259 APPARATUS FORCARRYING OUT WELL DRILLING OPERATIONS FROM FLOATING STRUCTURES LafayetteE. Gilreath, Houston, Tex., assignor to Offshore EngineeringCorporation, a corporation of Delaware Filed Mar. 3, 1966, Ser. No.531,411 3 Claims. (Cl. 267-1) ABSTRACT OF THE DISCLOSURE Suspensionmechanism for supporting a drilling string from a floating platform toallow the platform to move vertically under the influence of wave actionwhile maintaining the string in engagement with the bottom of a wellbore during a well drilling operation. The invention includes extensiblemechanism of the cylinder and piston type connected to the string andplatform to yieldingly support the string and means for varying thepressure of fluid applied to the cylinder and piston in response tochanges in the weight of the drilling string during the progress of thedrilling operation to maintain the weight applied to the drilling bitsubstantially constant. The mechanism also embodies means formaintaining the piston and cylinder constantly lubricated bycontinuously supplying lubricant to the external suriace of the pistonand the surrounding internal surface of the cylinder.

This invention relates to the drilling of wells beneath the surface ofwater, and more particularly to apparatus for supporting a drillingstring from a floating structure during the drilling of a well underwater.

In the drilling of wells by the use of a rotary drilling string somemeans must be provided for supporting the string to control the weightwhich is applied to the drilling bit, and when such operations arecarried out under water by the use of floating structures it isnecessary that the string be suspended in a manner to prevent poundingof the drilling bit on the bottom of the bore due to vertical movementsof the string with the floating structure resulting from wave action.

The present invention has for an important object the provision ofsuspension mechanism for supporting a drilling string on a floatingstructure embodying means whereby the structure may move verticallyunder the influence of wave action while maintaining the downward forceexerted on the drilling bit substantially constant.

Another object of the invention is to provide suspension mechanism forsupporting a drilling string on a floating platform, including cylinderand piston means forming an extensible and retractable connectionbetween the platform and string, and embodying means for maintainingsubstantially constant pressure of fluid in the cylinder while allowingvariations in the volume of such fluid due to vertical oscillation ofthe platform resulting from wave action, whereby the downward force ofthe string on the drilling bit may be maintained substantially constant.

A further object of the invention is the provision in drilling stringsuspension mechanism of the kind referred to of means for varying thepressure of fluid applied to the cylinder and piston means in accordancewith changes in the weight of the drilling string during the progress ofthe drilling operation to maintain the weight applied to the drillingbit substantially constant.

A still further object of the invention is to provide a cylinder andpiston arrangement for use in the suspension of a rotary drillingstring, which is constructed to withstand the high weight loads andfluid pressure required in apparatus of such character, and in whichmeans is embodied for the continuous supplying of lubricant to thecylinder and piston.

The above and other important objects and advantages of the inventionwill be apparent from the following detailed description of a preferredembodiment of the same when considered in conjunction with the annexeddrawings, wherein:

FIGURE 1 is a perspective view of the suspension apparatus of theinvention adapted to be supported on a floating structure and connectedto a drilling string to support the same therefrom while allowingvertical movements of the supporting structure relative to the string;

FIGURE 2 is a fragmentary view, partly broken away and partly incross-section and on a greatly enlarged scale, of a preferred embodimentof the cylinder and piston mechanism by which the drilling string isconnected to and supported from the floating structure; and

FIGURE 2A is a fragmentary view, partly in crosssection, and on agreatly enlarged scale showing the upper end portion of the cylinder andpiston apparatus, FIGURE 2A being an upward extension of the apparatusshown in FIGURE 2.

Referring now to the drawings in greater detail the apparatus of theinvention is intended primarily for use on a floating structure, such asa drilling barge, or the like, not shown, which is furnished withupright support means such as a conventional derrick, or the like, orwhich may conveniently be of the form illustrated in FIGURE 1 whereinthe support is generally designated 10, having the uprights 12, suitablysecured to the platform of the floating structure, as by means of baseblocks 14, and suitable braces, such as those shown at 16, and whichcarry at their upper ends a cross frame 18.

Suitable travelling block mechanism, designated 20 is carried by a cable22, supported on the cross frame and which leads to the usual cablewinding mechanism 24 mounted on the platform.

Rotary table mechanism 26, of the usual type is located on the platformbetween the uprights 12 which is adapted to rotate a kelly 28, or thelike, by which a drilling string extending downwardly from the floatingstructure may be rotated to drill a hole in the earth formation beneaththe water.

The travelling block 20 is provided with the usual hook 30, or the like,by which it is connected to an elevator 32, of a well known kind, andthe kelly 28 is attached at its upper end to the usual rotatableconnection 34 by which a hose 36 is attached to the kelly through whichwell fluid is supplied to the drilling string during the drillingoperation.

A return hose 38 is connected to a fitting 40 which is in communicationwith the usual casing which surrounds the drilling string and throughwhich well fluid is returned upwardly from the well bore.

The above described drilling mechanism is of a well known type and formsno part of the present invention but is included here for the purpose ofmore fully disclosing the nature and intended use of the same.

The apparatus of the present invention includes an elongated mainpressure cylinder 42, having at its lower end a hook 48 by which thecylinder is connected to the swivel 34, and Within the cylinder a pistonis movably disposed, having a piston rod 44 which is connected at itsouter end to the elevator 32.

The pressure cylinder mechanism is thus connected between the travellingblock 20 and the kelly 28 so that upon the application of a sufficientlyhigh pressure of fluid to the cylinder 42 above the piston therein, theweight of the drilling string, or a desired portion of such weight willbe supported by the fluid.

The cylinder 42 of the pressure cylinder mechanism is closed at itslower end by a screw plug 46 of which the hook 48 forms a part, the plugbeing conveniently threaded into an internally threaded sleeve 50, whichin turn is threadably connected to the lower end of the cylinder. At itsupper end the cylinder is provided with a cap 52 threadably connectedthereto, and which has a central opening 54 through which the tubularpiston rod 44 is slidably extended, the cap being provided with suitablepacking, such as that shown at 56 to form a fluid tight seal between thecap and rod.

Within the cylinder 42 a piston 58- surrounds the lower end of the rod44, to which the piston is attached, as by means of a ring 60 having aninternally shouldered portion 62 against which the lower end of the rod44 is seated and attached by means of screws 64. The ring 60 is securedto the piston by screws 66.

The plug 46 is provided with a passageway 68 through which fluid in thecylinder 42 beneath the piston 58 may escape upon downward movement ofthe piston relative to the cylinder and also through which fluid fromthe exterior may enter the cylinder beneath the piston when the pistonmoves upwardly relative to the cylinder.

The tubular piston rod 44 is closed at its lower end by a plug 70 whichseats. on the internally shouldered portion 62 of the ring 60 and whichhas a passageway 72 in communication with a passageway 74 in the pistonthrough which lubricant is supplied between the external surface of thepiston and the surrounding internal surface of the cylinder.

Suitable packing is provided, such as that shown at 76, on the piston toform a seal between the piston and the surrounding wall of the cylinder.The piston also has a central extension 78 formed with a counterbore 80of larger diameter than and into which the piston rod 44 is extended,and within which the piston rod has openings 82 through which fluid mayflow into and out of the cylinder above the piston through the pistonrod.

At its upper end the piston rod 44 has an externally enlarged cap 84formed with a downwardly tapering external surface 86 for engagementwith the elevator 32 by which the pressure cylinder mechanism issupported. The cap 84 has a central bore 88 in communication with theinterior of the piston rod and is provided with a side port 90 which isinternally threaded for the attachment thereto of a hose connectionfitting 92 to which a pressure base 94 is connected to conduct pressurefluid into and out of the cylinder through the piston rod.

The cap 84 also has a central opening 96 therethrough, through which alubricant pipe 98 is extended, whose upper end is connected into alubricant reservoir 100, which is threadably attached to the cap. Thepipe 98 extends downwardly in the piston rod 44 and is threadablyconnected at its lower end to the plug 70 in communication with thepassageway 72 to allow lubricant to flow to the external surface of thepiston which is in sliding contact with the surrounding wall of thecylinder.

A cylinder 102 of relatively small diameter, called a repeating cylinderis suitably supported on and extends longitudinally alongside of themain cylinder 42. The repeating cylinder has a piston movably disposedtherein to which a piston rod 104 is connected which is also suitablyconnected to the piston rod 44, externally of the main cylinder, as seenat 106 in FIGURE 1, whereby extension and contracting movement oroscillations of the main cylinder mechanism are repeated by therepeating cylinder. The lower end of the repeating cylinder is connectedat its lower end by a pressure line or hose 108 with a suitableinstrument designated 110 in FIGURE 1 which indicates changes in theposition of the piston in the repeating cylinder whereby oscillations ofthe main cylinder mechanism may be readily observed.

For the purpose of maintaining a desired pressure in the main cylinder42 above the piston 58 to support the weight of the drilling string, apressure accumulator, generally designated 112 in FIGURE 1 is provided,which may be made up of a number of heavy walled pressure cylindersforming a battery of large volume, so that relatively large variationsin the volume in the main cylinder 42 may take place without causing anysubstantial change in the pressure in the accumulator.

Air compressor mechanism 114 of relatively large capacity, which may beof the dual compressor type, is provided for replenishing the! fluid inthe accumulator and maintaining the pressure therein at the desiredvalue. The compressor is connected into the system to supply pressure tothe accumulator in the usual manner, as by means of pressure fluid lines116 and 118 under the control of suitable pressure regulator 120 ofconventional type which is controlled from a control panel 122 through apressure line 124 in a well known manner, as by means of a hand lever125. The pressure of the fluid supplied by the compressor is indicatedby a pressure gauge 126 on the panel 122 through a pressure line 128.The pressure supplied to the system from the accumulator is indicated onthe panel 122 through a pressure line 130, by gauges 129 and 131.

Pressure is supplied to the cylinder 42 through a line 132 leading fromthe regulator 120 to the hose 94.

An auxiliary pressure line 134 may also be provided for supplying fluidunder pressure for the operation of any other desired equipment.

Under some circumstances it may be desired to provide additionalaccumulators, not shown, and for this purpose a pressure line 136 may beprovided leading to an indicator 138 on panel 122.

In the operation of the apparatus, constructed and arranged as describedabove, a drilling string is attached to the kelly 28 to be supported onthe swivel 34 for rotation by the rotary table 26. The cylinder 42 isthen pressurized to support the weight of the string, or a desiredproportion thereof with the drill in engagement with the bottom of thewell bore.

The drilling operation is then carried out in the usual manner andduring such operation vertical movements of the floating structure fromwhich the string is suspended will result in variations in the volume ofthe fluid in the cylinder 42. A substantially constant downward force onthe bit will be exerted due to the mantenance of a relatively smallpressure differential resulting from the variations in the volume of theair in the cylinder in response to vertical movements of the floatingstructure. Upon downward movement of the floating structure an increasein the volume of the fluid in the cylinder 42 will take place, and uponupward movement of the floating structure a corresponding decrease insuch volume will occur. By providing an accumulator having a relativelylarge volume, however, very little change in pressure will take place,so that the downward force exerted by the drilling string will remainsubstantially constant. Moreover, the drilling string will remain incontact with the bottom of the well bore during the drilling operationwhich is carried out in the usual manner by lowering the string byoperation of the winding mechanism of the cable 22 as the drillingprogresses.

When it becomes necessary to add sections of pipe to the drillingstring, this may be accomplished in the usual manner, the pressure inthe cylinder 42 being suitably adjusted by the operator to compensatefor the additional weight thus added to the string.

By carefully checking the changes in the positio of the piston 58, asindicated on the indicator associated with the repeating cylinder 102,the extent of the vertical movement of the vessel relative to thedrilling string may be readily determined. The pressure which is appliedto the cylinder 42 may also be carefully regulated by suitable actuationof the control lever 125, to maintain the piston therein at apredetermined location as indicated by the gauge 110 of the repeatingcylinder 102, to properly support any load on the string and maintainthe same at the same vertical location during the drilling operation.

It will thus be seen that the invention, constructed as described aboveprovides suspension mechanism which is particularly useful for thesuspension of a drilling string from a floating structure and by whichthe string may be supported against vertical oscillation while allowingvertical movement of the supporting structure due to wave action.

Having thus clearly shown and described the invention, what is claimedas new and desired to secure -by Letters Patent is:

1. Well equipment suspension apparatus comprising,

a cylinder,

a piston movable disposed in the cylinder for longitudinal androtational movement therein,

a hollow piston rod connection to said piston for movement therewithextending to the exterior of the cylinder and in communication with theinterior of the cylinder at one side of said piston,

means for connecting one of said cylinder and piston rod to a supportabove a well bore,

means for connecting the other of said cylinder and piston rod toequipment to be suspended in the bore,

means for connecting said piston rod in communication with a source offluid under pressure to position the piston at a location to suspendsaid equipment in said bore, and

means 'for introducing a lubricant into said cylinder at a locationbetween said piston and the surrounding internal surface of saidcylinder.

2. The apparatus as specified in claim 1 wherein said piston is formedwith a passageway opening at one end to the exterior of the piston at alocation opposite the surrounding wall of the cylinder, and meansextending into said piston rod and in communication with said passagewayfor introducing a lubricant into said passageway.

3. The apparatus as specified in claim 1 and including means forindicating the position of the piston in the cylinder including movablemeans connected to said piston for movement therewith and pressureresponsive means for indicating the position of said movable means.

References Cited UNITED STATES PATENTS 2,259,019 10/ 1941 Carr et al. 267-1 2,842,226 7/1948 Liebel 188-264.1 2,945,677 7/ 1960 Kammerer 26713,227,433 1/1966 Greer 26764 3,315,902 4/1967 Pollitz 267-65 X DRAYTONE. HOFFMAN, Primary Examiner.

US. Cl. X.R.

